7-ACA is a key intermediate compound in the synthesis of many semi-synthetic cephalosporin antibiotics. It may e.g. be produced from cephalosporin C by cleavage of the amide function in position 7 of the ring sytem
e.g. chemically, e.g. by conversion of the amide function into an imide chloride function which may be hydrolysed to give 7-ACA, e.g. in a strong acidic medium and precipitating 7-ACA, e.g. by adjustment of the pH (around the isoelectric point), e.g. by addition of a base; 7-ACA may be isolated in the form of rosettes and agglomerates;
or enzymatically, e.g. by action of an acylase; or by conversion of cephalosporin C into glutaryl-7-amino-cephalosporanic acid, e.g. by action of a D-amino acid oxidase, enzymatically hydrolysing a glutaryl-7-amino cephalosporanic acid to obtain 7-ACA, e.g. in a basic medium, neutral or slightly acidic medium, optionally purifying the reaction solution with an appropriate ion exchanger or adsorber resin, and precipitating 7-ACA, e.g. by adjustment of the pH (around the isoelectric point), e.g. by addition of an acid, e.g. HCl. In that case precipitated 7-ACA may be, however, in the form of very small, loose, needle-like crystals difficult to be isolated. Increasing purity of 7-ACA may result in still smaller crystals and addition of an organic solvent, e.g. a, e.g. lower, alcohol, e.g. methanol or a ketone, e.g. acetone, to the reaction mixture before the isolation of 7-ACA, which may improve the yield, again may result in considerably smaller crystals.
The present invention provides a process, e.g. which may by carried out on technical scale, wherein agglomerates or rosettes of 7-ACA may be formed on 7-ACA precipitation from an alkaline, neutral or slightly acidic medium which substantially improves isolation of 7-ACA, e.g. by filtration and centrifugation and additionally, 7-ACA obtained according to the present invention may be dried more quickly, e.g. which may result in a smaller amount of by-products compared with 7-ACA obtained according to a prior art process.
In one aspect the present invention provides a process for the production of rosettes or agglomerates of 7-ACA, e g. of formula I, characterized in, that 7-ACA is precipitated from an alkaline, neutral or slightly acidic medium in the presence of an additive, e.g. selected from a group comprising e.g. groups as defined below.
An additive according to the present invention may be a compound which on addition in a precipitation process of 7-ACA may cause formation of agglomerates and/or rosettes includes e.g. organic carboxylic acid esters,e.g. of formula
R1xe2x80x94COOxe2x80x94R2xe2x80x83xe2x80x83II,
polymeric glycols, e.g. polyethylene and polypropylene glycols, e.g of formula
HOxe2x80x94(CHR1xe2x80x94CHR2)kxe2x80x94OHxe2x80x83xe2x80x83III,
polyacryls, e.g. of cationic, anionic or non-ionic polyacryls, including e.g. polacrylamides, e.g. of formula
xe2x80x94[CHR1xe2x80x94CR2(COXR3)]nxe2x80x94xe2x80x83xe2x80x83IV,
amines and polyamines, e.g. of formulae
xe2x80x94[CH2xe2x80x94CHR6xe2x80x94CH2xe2x80x94N+R1R2xe2x80x94]nxe2x80x94xe2x80x83xe2x80x83Va
R2R4Nxe2x80x94(CH2xe2x80x94CH2X)nxe2x80x94R5xe2x80x83xe2x80x83Vb
[R1xe2x80x94Xxe2x80x94(CH2)m]3Nxe2x80x83xe2x80x83Vc

melamin-formaldehyde resins, e.g. of formula 
e.g. of a molecular weight of up to 1,000,000, e.g. 500,000 and amino acids and esters thereof, e.g. of formula
xe2x80x83R10xe2x80x94CHxe2x80x94(NR2R4)xe2x80x94COOR1xe2x80x83xe2x80x83VIII
e.g. including mixtures of individual additives, e.g. as described above. An additive may be preferably an amino acid and esters therof, e.g. an amino acid such as e.g. lysine.
In formulae II, III, IV, Va, Vb, Vc, VIa, VIb, VII and VIII
R1, R2, R4 and R5 independently of each other denote hydrogen, alkyl or aryl;
k denotes a whole number from 2 to 200;
X denotes xe2x80x94Oxe2x80x94 or xe2x80x94NR1xe2x80x94;
R3 has the meaning of R1 or denotes a group of formula xe2x80x94(CR2R4)mxe2x80x94Z
Z denotes amino, a sulphonyl group or a carboxylic acid group, e.g. of formulae 
m denotes a whole number from 0 to 6;
n denotes a whole number from 2 to 200,000;
R6 represents hydrogen or hydroxy;
R7a, R7b, R7c, R7d and R7e independently of each other denote hydrogen, xe2x80x94CH2OH; or a group of formula 
and R10 denotes hydrogen, alkyl, aryl or a group of formula xe2x80x94(CH2)mxe2x80x94Xxe2x80x94R5.
If not otherwise defined herein, alkyl includes e.g. (C1-22)alkyl, such as (C1-8)alkyl, e.g. lower alkyl, such as (C1-4)alkyl and aryl includes e.g. phenyl, naphthyl, such as phenyl.
Alkyl and aryl includes unsubstituted alkyl and aryl and alkyl and aryl substituted by groups which do not cause the formation of another compound than 7-ACA under precipitation conditions of 7-ACA in alkaline, neutral and slightly acidic medium; e.g. which do not chemically react with 7-ACA to form another compound. Preferably alkyl includes lower alkyl; aryl includes phenyl and substituted aryl includes substituted aryl, e.g. phenyl by hydroxy or alkyl e.g. lower alkyl. Amino includes unsubstituted amino or ammonium and substituted amino and ammonium, e.g. by alkyl.
In another aspect the present invention provides a process for the isolation of 7-ACA, e.g. of formula I from slightly acidic, neutral or alkaline solution, characterized in that 7-ACA is precipitated in the presence of an additive, e.g. selected from a group comprising groups as e.g. defined above, e.g. in an amount of 1 ppm to 10% in the slightly acidic, neutral or alkaline solution.
A process of the present invention may be carried out as follows:
7-ACA may be precipitated
from slightly acidic, neutral or alkaline solution of 7-ACA, including e.g. a solution of 7-ACA in a solvent to which an acid is to be added for precipitating 7-ACA therefrom, e.g. a solution of 7-ACA having a pH which is above the isoelectric point of 7-ACA in a solvent; which is in contrast to a strong acidic solution of 7-ACA to which a base is to be added for precipitating 7-ACA therefrom, e.g. a solution of 7-ACA having a pH which is below the isoelectric point of 7-ACA in a solvent
in the presence of an additive, e.g. selected from a group comprising groups as defined above, e.g. in the presence of seed crystals of 7-ACA, e.g. in the form of rosettes and/or agglomerates by addition of an acid.
An additive according to the present invention is known or may be produced analogously to known, e.g. conventional processes. A slightly acidic, neutral or alkaline solution of 7-ACA may be obtained e.g. by an enzymatic process as defined above. The concentration of 7-ACA in slightly acidic, neutral or alkaline solution is not critical and may vary within a broad range, including e.g. a rangeof, e.g. ca., 5 to 60 g/l, such as 10 to 50 g/l. An additive may be e.g. added to 7-ACA in slightly acidic, neutral or alkaline solution before addition of an acid or simultanously.
The amount of an additive according to the present invention is not critical, e.g. for ecological reasons a low amount of an additive, e.g. ca., 1 ppm to 10% (v/v) in respect with the amount of 7-ACA solution may be appropriate. In case of use of non-polymeric additives, such as e.g. organic esters as an additive an amount of, e.g. ca., 1% to 10% may be appropriate; in case of use of an amine, amino acid or ester thereof an amount of, e.g. ca., 0.01% to 10%, such as, e.g. ca., 0.05% to 5% may be appropriate, in case of use of a polymeric additives, e.g. such as polyacryls, polyamines, polymeric glycols e.g. ca. 1 to 100 ppm may be appropriate. Seed crystals of 7-ACA, e.g. as defined above, may be added to a solution or to a resulting crystal suspension of 7-ACA either prior to or simultaneously with an acid.
The process of the present invention may be carried out batchwise or continuously, in a broad temperature range, including e.g. xe2x88x9215xc2x0 to 40xc2x0 C., such as 0xc2x0 to 25xc2x0 C.
An appropriate acid includes inorganic acids, e.g. sulphuric acid, hydrochloric acid or phosphoric acid, or organic acids, e.g. acetic acid.
The acid is added in an amount which is sufficient that 7-ACA, e.g. in high yields, is precipitated from the solution. A pH of the reaction mixture of around the isoelectric point of 7-ACA in a solvent may be convenient, including, but not limited to, a pH of 2.5 to 6, such as 3.5 to 5.5. 7-ACA may precipitate on acid addition, e.g. in crystalline form. A crystall suspension obtained may be stirred, e.g. under adjustment of the pH around the isoelectric point in order to complete precipitation, e.g. under cooling.
7-ACA obtained, e.g. in crystalline form and in the form of agglomerates and/or rosettes may precipitate and may be isolated, e.g. as conventional, such as by filtration, centrifugation, washed as appropriate and dried. The drying temperatures may be low, e.g. 40xc2x0 to 50xc2x0, e.g. under vacuum, and the drying times may be short, e.g. ca. 5 to 30, such as 10 to 20 hours.
The presence of an additive according to the present invention in the precipitaion of 7-ACA may surprisingly result in the formation of agglomerates or rosettes of 7-ACA, even in case that an organic solvent such as an alcohol or a ketone is present in the solution and even in case that highly pure 7-ACA, e.g. purified via an adsorber resin purification, e.g. with Amberlite XAD 1600R, XE-714R, Dianion HP21R, Sepabeads SP825R, SP850R), or via an ion exchanger purification, e.g. with IRA 420R. The filtration time of a 7-ACA crystal suspension in the presence of an additive obtained according to the present invention may considerably be reduced in comparison with the filtration time of 7-ACA obtained without the presence of an additive, e.g. from ca. 15 minutes to 1 minute and even below, such as of ca. 0.4 minutes.